diff --git a/lib/filewatch/helper.rb b/lib/filewatch/helper.rb
index 21c54b7..fc691fb 100644
--- a/lib/filewatch/helper.rb
+++ b/lib/filewatch/helper.rb
@@ -1,69 +1,71 @@
-# code downloaded from Ruby on Rails 4.2.1
-# https://raw.githubusercontent.com/rails/rails/v4.2.1/activesupport/lib/active_support/core_ext/file/atomic.rb
+# code downloaded from Ruby on Rails 4.2.4
+# https://raw.githubusercontent.com/rails/rails/v4.2.4/activesupport/lib/active_support/core_ext/file/atomic.rb
 require 'fileutils'
 
-class File
-  # Write to a file atomically. Useful for situations where you don't
-  # want other processes or threads to see half-written files.
-  #
-  #   File.atomic_write('important.file') do |file|
-  #     file.write('hello')
-  #   end
-  #
-  # If your temp directory is not on the same filesystem as the file you're
-  # trying to write, you can provide a different temporary directory.
-  #
-  #   File.atomic_write('/data/something.important', '/data/tmp') do |file|
-  #     file.write('hello')
-  #   end
-  def self.atomic_write(file_name)
+module FileWatch
+  class File < ::File
+    # Write to a file atomically. Useful for situations where you don't
+    # want other processes or threads to see half-written files.
+    #
+    #   File.atomic_write('important.file') do |file|
+    #     file.write('hello')
+    #   end
+    #
+    # If your temp directory is not on the same filesystem as the file you're
+    # trying to write, you can provide a different temporary directory.
+    #
+    #   File.atomic_write('/data/something.important', '/data/tmp') do |file|
+    #     file.write('hello')
+    #   end
+    def self.atomic_write(file_name, temp_dir = Dir.tmpdir)
+      require 'tempfile' unless defined?(Tempfile)
+      require 'fileutils' unless defined?(FileUtils)
 
-    if File.exist?(file_name)
-      # Get original file permissions
-      old_stat = stat(file_name)
-    else
-      # If not possible, probe which are the default permissions in the
-      # destination directory.
-      old_stat = probe_stat_in(dirname(file_name))
-    end
-
-    mode = old_stat ? old_stat.mode : nil
-
-    # Create temporary file with identical permissions
-    temp_file = File.new(rand_filename(file_name), "w", mode)
-    temp_file.binmode
-    return_val = yield temp_file
-    temp_file.close
+      temp_file = Tempfile.new(basename(file_name), temp_dir)
+      temp_file.binmode
+      yield temp_file
+      temp_file.close
 
-    # Overwrite original file with temp file
-    File.rename(temp_file.path, file_name)
+      if File.exist?(file_name)
+        # Get original file permissions
+        old_stat = stat(file_name)
+      else
+        # If not possible, probe which are the default permissions in the
+        # destination directory.
+        old_stat = probe_stat_in(dirname(file_name))
+      end
 
-    # Unable to get permissions of the original file => return
-    return return_val if old_stat.nil?
+      # Overwrite original file with temp file
+      FileUtils.mv(temp_file.path, file_name)
 
-    # Set correct uid/gid on new file
-    chown(old_stat.uid, old_stat.gid, file_name) if old_stat
-
-    return_val
-  end
+      # Set correct permissions on new file
+      begin
+        chown(old_stat.uid, old_stat.gid, file_name)
+        # This operation will affect filesystem ACL's
+        chmod(old_stat.mode, file_name)
+      rescue Errno::EPERM, Errno::EACCES
+        # Changing file ownership failed, moving on.
+      end
+    end
 
-  # Private utility method.
-  def self.probe_stat_in(dir) #:nodoc:
-    basename = rand_filename(".permissions_check")
-    file_name = join(dir, basename)
-    FileUtils.touch(file_name)
-    stat(file_name)
-  rescue
-    # ...
-  ensure
-    FileUtils.rm_f(file_name) if File.exist?(file_name)
-  end
+    # Private utility method.
+    def self.probe_stat_in(dir) #:nodoc:
+      basename = [
+          '.permissions_check',
+          Thread.current.object_id,
+          Process.pid,
+          rand(1000000)
+      ].join('.')
 
-  def self.rand_filename(prefix)
-    [ prefix, Thread.current.object_id, Process.pid, rand(1000000) ].join('.')
-  end
+      file_name = join(dir, basename)
+      FileUtils.touch(file_name)
+      stat(file_name)
+    ensure
+      FileUtils.rm_f(file_name) if file_name
+    end
 
-  def self.device?(file_name)
-    chardev?(file_name) || blockdev?(file_name)
+    def self.device?(file_name)
+      chardev?(file_name) || blockdev?(file_name)
+    end
   end
 end